* Move undo item copy global variable into schematic editor frame object
  member variable.
* Add helper methods for accessing the undo item copy member variable.
* Fix undetected bug when changing a text type.
* Added an exchange command to the undo/redo base class for handling undoing
  a changed item type which cannot be undone by swapping out the variables.
* Revert change to common/hotkeys_basic.cpp that broke hot key behavior.
* Lots of coding policy changes while making the changes above.